The present invention relates to a lifting insert for prefabricated concrete components with a bracket for increasing the shearing strength thereof.
In the field of the production of prefabricated concrete components, it is known to embed in the body of the component, during its casting, metallic inserts to be used to lift the component.
In order to achieve adequate anchoring in the concrete casting, these inserts are provided with brackets.
Brackets are divided into two categories: those for increasing pulling strength and those for increasing shearing strength.
Brackets for increasing pulling strength are constituted, in most cases, simply by substantially U-shaped brackets made of steel rod inserted in one or more holes provided in the lifting insert. The function of these brackets is to provide an ideal extension of the insert in the concrete body, thus achieving higher resistance to extraction by affecting larger concrete regions located further away from the insert. In this manner, the forces applied to the insert are distributed over larger surfaces, which leads to a reduction in specific stresses.
The shearing stress that occurs when a transverse force is applied to the insert, for example when tipping prefabricated components of the panel type, is more critical to neutralize, since such stress, which is generally perpendicular to the larger faces of the component, affects a very small thickness of the component and it is therefore more difficult to adopt a bracket capable of distributing said stress effectively.
It should also be noted that tipping of the components is required in order to extract them from the formwork, i.e., when the component has not yet acquired its full mechanical strength. In these occasions it is quite likely for the tipping of the component to cause the breakage of the concrete due to the action of the insert on the contiguous regions.
Brackets for increasing shearing strength can in turn be divided into two categories: brackets composed of contoured braces made of steel rod, which extend transversely to the insert on planes perpendicular to the direction of the force that generates the shearing stress in order to affect regions of the concrete that lie laterally with respect to the insert, and brackets constituted by plates welded to the insert.
In the first case, provision of the bracket is entrusted fully to the experience and skill of the operator and it is therefore difficult to obtain a constant and precise result. A slight variation in the position of the rod that constitutes the brace with respect to the insert, or in the shape of the rod, is in fact sufficient to lead to a considerably different shearing strength.
In the second case, the random variability of the positioning and shaping of the brace is eliminated, but there are other drawbacks, such as for example the higher cost of the bracket, higher costs for galvanization of the insert, which must also affect the plate, and higher costs for storage and transport, since the insert and the plate cannot be separated.
Another drawback of this last bracket is the different strength obtained depending on whether the shearing stress acts in one direction or in the opposite direction.
Moreover, the welded plate generates a discontinuity in the body of the concrete component in a low-thickness region and accordingly can cause the separation of portions of concrete, reducing its overall strength.
The aim of the present invention is to solve the above mentioned problems, by providing a lifting insert for prefabricated concrete components with a bracket for increasing the shearing strength thereof, which can be arranged precisely with respect to the insert without necessarily having to weld it to the insert.
Within this aim, an object of the invention is to provide a lifting insert with a bracket that can be manufactured at a low cost.
Another object of the invention is to provide a lifting insert with a bracket that ensures substantially identical strength with shearing stresses acting in one direction or in the opposite direction.
Another object of the invention is to provide a lifting insert with a bracket that achieves high adhesion to the concrete, increasing the resistance of the insert against extraction from the concrete.
Another object of the invention is to provide a lifting insert with a bracket that can be increased simply and rapidly according to requirements.
This aim and these and other objects that will become better apparent hereinafter are achieved by a lifting insert for prefabricated concrete components with a bracket for increasing the shearing strength thereof, comprising an insert that can be embedded in the body of the component proximate to one of the faces of the component, said insert having an end that lies proximate to said face of the component and can be engaged by lifting means, at least one brace being provided which is connected to said insert and can be embedded with it in the body of the component, characterized in that said brace is constituted by a lamina that wraps around said insert in a scarf-like fashion with one of its portions.